An optimisation algorithm for designing fixed-structure controllers using the QFT method

We propose a simple optimisation algorithm for designing fixed-structure controllers for highly-uncertain plants. The method can be used to automate the loop-shaping step of the quantitative feedback theory (QFT) design procedure and guarantees robust stability and performance to the feedback loop for all parameters in the plant´s uncertainty set. To avoid over-designing the system, the algorithm can be used to minimise either the asymptotic gain or the cross-over frequency of the open-loop system. Some preliminary results of this work have appeared in Zolotas et al. (1999).